The present invention relates to a liquid crystal display device, and, more particularly, to a liquid crystal display device of the partial transmissive type, in which it is possible to eliminate a frame-like luminance difference around the periphery of the light transmissive region in each pixel.
A liquid crystal display device of the partial transmissive type is used as a miniaturized liquid crystal display device for a mobile telephone or the like. This liquid crystal display device allows a user to recognize images on a display screen using light made up of the reflective light of the sun (a light reflection mode) or using light from a backlight incorporated in the liquid crystal display device (a light transmissive mode), depending on the conditions existing at the locations where the liquid crystal display device is being used.
That is, in a typical liquid crystal display device, a pair of transparent substrates are arranged to face each other in an opposed manner with a liquid crystal layer disposed therebetween. On a liquid-crystal-side surface of one transparent substrate, regions which are defined by gate signal lines which extend in the x direction and are juxtaposed in the y direction and drain signal lines which extend in the y direction and are juxtaposed in the x direction constitute pixel regions. In each pixel region, there is a switching element, which is driven by supplying a scanning signal from one gate signal line, and there is a pixel electrode to which a video signal is supplied from one drain signal line through the switching element.
The pixel electrode is formed of a light transmissive conductive layer made of ITO (Indium-Tin-Oxide), for example, in one region of the pixel region, and it is formed of a non-light transmissive conductive layer, such as a metal layer made of Al or the like, in the remainder of the pixel region. An electric field is generated between the pixel electrode and a counter electrode, which is formed in common with respective pixel regions and is formed of a light transmissive conductive layer on a liquid-crystal-side surface of the other transparent substrate, whereby the liquid crystal within the pixel region is activated in response to the electric field. In this case, a portion of the pixel area in which the light transmissive pixel electrode is formed is used as a light transmissive region and a portion of the pixel area in which the non-light transmissive pixel electrode is formed is used as a light reflective region.
Further, in a liquid crystal display device having such a constitution, there is a known technique in which the pixel electrode formed of the light transmissive conductive layer is arranged below an insulation film, a hole is formed in the insulation film in a region corresponding to the light transmissive region so as to expose the pixel electrode formed of the light transmissive conductive layer, and a pixel electrode formed of the non-light transmissive conductive film is formed in a region above the insulation film and outside the light transmissive region, that is, in the light reflective region.
Here, the reason why the hole is formed in the region corresponding to the light transmissive region of the insulation film is to make the length of an optical path of light which passes through the liquid crystal in the light transmissive region substantially equal to the length of an optical path of light which passes through the liquid crystal in the light reflective region.